A good golf swing is a product of the control of a multitude of factors. Of these factors, perhaps the most critical is the swing path of the club head slightly before contact with the golf ball until just after the contact, in a path range known as the "hitting zone."
In a correct swing, the club head generally traces a tilted circle through the air, moving inward toward the golfer and upward on the backswing and, on the return downswing, passing through the point of impact with the ball at approximately the location where the tilted circle meets the ground, before moving upward and inward into the finish of the swing.
Devices have been developed to train the golfer to follow the ideal tilted circle in his swing until muscle memory is developed to "groove" the swing. One device includes an actual tilted circular structure against which the club shaft slides during the complete swing motion. However, such devices do not necessarily permit the golfer to develop the correct body motions to perform a correct swing without the presence of the support surface.